Color photographic elements typically contain three records sensitive to regions of the spectrum corresponding to red, green and blue light. The records also contain dye forming compounds which are typically cyan in the red sensitive record, magenta in the green sensitive record and yellow in the blue sensitive record. The dyes are produced from the compounds during color development (the only color developer in color negative development, and the second developer in color reversal development). In order to accurately reproduce colors, each of the three records should ideally be sensitive only to light of one color and, in addition, the dye formed in each record should only absorb light of the same color to which the record is sensitive. However, the dyes typically also absorb some light of another color. For example, cyan dyes typically also absorb some green light.
Another defect in color reproduction arises because, during color development of the three color image-forming emulsion layers, the development of an image in one of the layers may cause unwanted formation of color in an adjacent emulsion layer intended by definition to record another image. For example, the development of the magenta image of the green-sensitive layer may cause formation of cyan dye in the red-sensitive layer, but following the pattern of the magenta image. This defect results from the fact that the oxidation products of development of one of the layers may diffuse to an adjacent layer where they would give rise to an unwanted coupling with the coupler present in this layer.
While development inhibitor releasing compounds ("DIR" compounds) in the form of couplers have been employed successfully in negative photographic elements to correct the above defects, they have met very limited success in reversal photographic elements. One of the reasons for this is that negative elements are only processed in a color developer to produce a negative dye image. On the other hand, reversal elements are first processed in a black and white developer followed by a fogging step, then a color developer. Currently, the standard process for processing reversal films,is by Kodak Process E-6 development described in more detail below, or substantially equivalent processes made available by other manufacturers. Such processes use exhaustive color development. As described by T. H. James, ed., The Theory of the Photographic Process, 4th Edition, Macmillan, New York, 1977, page 611, exhaustive color development results in DIR couplers having little effect in color reversal materials. Similarly, U.S. Pat. No. 4,788,132 states that the use of a DIR coupler in color reversal materials does not produce any substantial interimage effect since color development is hardly inhibited. While U.S. Pat. No. 4,729,943 describes the use of DIR couplers in color reversal elements, the DIR coupler is incorporated in a layer which does not take part in image formation and the color development time is reduced to between 1 and 2 minutes (that is, the development process is non-standard).
For purposes of this invention, conventional development processes include the E-6 process as described in Manual For Processing Kodak Ektachrome Films Using E-6, (1980) Eastman Kodak Company, Rochester, N.Y., Or a substantially equivalent process made available by a company other than Eastman Kodak Company, are referred to as "current" color reversal processes or "standard" processes. Current reversal processes employ as a color developer, 4-(N-ethyl-N-2-methylsulfonylaminoethylino)-2-methylphenylenediamine sesquisulfate, 1-hydrate in a concentration of from about 7 to about 11 grams per 1000 ml of water, and as a silver halide solvent, 2,2-ethylenedithioethanol (also known as Dithiaoctanediol) in a concentration of about 0.6 to about 1.2 grams per 1000 ml of water. The pH of the color developing agent is from about 11.6 to about 12.1. The color developing agent is used in the process for about from 5.5 to 7.0 minutes at a temperature of from 36.6 to 39.4 C.
It should be noted at this point that color reversal films have higher contrasts and shorter exposure latitudes than color negative film. Reversal films have a gamma generally between 1.5 and 2.0, and this is much higher than for negative materials. Moreover, such reversal films do not have masking couplers, and this further differentiates reversal from negative working films.
One method that has been particularly used in color reversal to obtain an interimage effect, is adjustment of the composition of halides, in particular iodide ion, used in different layers of the element. This produces an interimage effect during the black and white development step by action of the iodide ions released from the developing silver haloiodide emulsions. Another method described in U.S. Pat. No. 4,082,553 is the use of fogged grains in a receiver layer (a "receiver" layer being one which receives the interimage effect). However, the use of fogged grains requires additional silver laydown to compensate for reduced density which in turn reduces the effective speed of the record.
It would be desirable then to provide a means which provides high interimage effect, particularly in color reversal elements, and which allows a reversal element to be processed by standard processing methods but which does not solely rely on the use of fogged grains.